<style>
body { margin: 0; padding: 0; }

div {
  display: inline-flex;
  width: 50px;
  height: 50px;
  border-right: 1px solid black;
  border-bottom: 1px solid black;
}
</style>
  
<body></body>

<script>
const colors = ['#222', '#444', '#666', '#888', '#aaa'];
for (let i = 0; i < 200; ++i) {
  const div = document.createElement('div');
  div.style.setProperty('background-color', colors[i % 5]);
  document.body.appendChild(div);
}
</script>
